Burn through resistant systems for transportation, especially aircraft

ABSTRACT

An encapsulated insulation composite system for increasing the burn through resistance of an aircraft fuselage includes: an insulation layer of glass fiber or foam insulation and a coating or interleaf barrier layer of a high temperature resistant material and/or a coating or barrier layer of a high temperature resistant material on an outer major surface of the insulation layer of the composite and a film encapsulating the composite. Preferably, the barrier layer or layers include a reflective mineral, such as a reflective mineral containing coating carried on a sheet material. Preferably, the encapsulating film is a polymeric film such as a polyimide film.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an insulation system foraircraft fuselages and, in particular, to an insulation system forincreasing the burn through resistance of aircraft fuselages to providepassengers with additional time within which to evacuate an airplane inthe event of an external fuel fire.

[0002] Currently, the Federal Aviation Administration (the FAA) istesting various aircraft fuselage sidewall constructions to determine ifthey can demonstrate a significant increase in burn through resistancein a simulated exterior fire condition. For example, the test simulatesa situation where the aircraft is on the ground and a jet fuel fireignites next to the outside of the fuselage.

[0003] The baseline fuselage sidewall construction in current usecombines an interior trim panel with one or more layers of Microlite AAfiberglass insulation blanket, encapsulated in a reinforced Mylar film,that is positioned in the framework of an aircraft with an exterioraluminum skin. The fiberglass blanket currently used in the baselineconstruction is 0.42 pound per cubic foot (pcf)×1 inch (6.7 Kg/m³×25.4mm) or 0.6 pcf×1 inch (9.6 Kg/m³×25.4 mm) Microlite AA. In someconstructions used by aircraft manufacturers, one or all of theMicrolite AA fiberglass blanket layers are replaced with a 0.3 pcf×1inch to a 0.6 pcf×1 inch (4.8 Kg/m³×25.4 mm to 9.6 Kg/m³×25.4 mm)polyimide foam.

[0004] In a real or simulated fire condition, all of the individualfuselage components melt away quickly and permit flame to penetrate intothe passenger compartment. The baseline fuselage construction typicallyprovides only a couple of minutes of burn through protection in thesetests. There are many ways to improve burn through protection in anaircraft fuselage. However, the most obvious solutions require asignificant addition of weight which is undesirable in aircraftconstruction.

SUMMARY OF THE INVENTION

[0005] By replacing the current two to three layers of 0.42 pcf×1 inch(6.7 Kg/m³×25.4 mm) or 0.6 pcf×1 inch (9.6 Kg/m³×25.4 mm) Microlite AAblanket insulation system, described above, with the burn throughresistant system of the present invention, the length of time it takesto burn through the insulation portion of the system has been shown toincrease from a couple of minutes to more than five minutes andpreferably more than 7 minutes. The burn through resistant system of thepresent invention has one or more coating or interleaf layers of hightemperature resistant material included in the encapsulated multilayeredconstruction of fiberglass blanket layers and/or foam insulation layers.

[0006] To provide good results in the simulated fire condition of a fullscale FAA simulated burn through test, the system must also be able towithstand moderate air pressure fluctuations attributed to the pulsingflame front or wind. The burn through resistant system of the presentinvention is able to withstand such moderate air pressure fluctuations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a schematic cross section through a first embodiment ofthe burn through resistant system of the present invention installed ina fuselage with one coating or interleaf layer of high temperatureresistant material intermediate insulation layers of the system.

[0008]FIG. 2 is a schematic cross section through a second embodiment ofthe burn through resistant system of the present invention installed ina fuselage with two coating or interleaf layers of high temperatureresistant material intermediate insulation layers of the system.

[0009]FIG. 3 is a schematic cross section through a third embodiment ofthe burn through resistant system of the present invention installed ina fuselage with a coating or interleaf layer of high temperatureresistant material among an insulation layer and the encapsulatingenvelope of the system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] As shown in FIG. 1, a first embodiment of the burn throughresistant system 20 includes a plurality of glass fiber insulationblanket layers and/or foam insulation sheet layers 22 and one hightemperature resistant material coating or interleaf layer 24intermediate two of the insulation layers 22. The glass fiber insulationblanket layers and/or foam insulations sheet layers 22, along with thehigh temperature resistant material coating or interleaf layer 24, areencapsulated or enclosed within an envelope 26 and placed against oradjacent the skin 28, e.g. aluminum skin, of the aircraft fuselage 30.As shown in FIG. 2, a second embodiment of the burn through resistantsystem 20 includes a plurality of glass fiber insulation blanket layersand/or foam insulation sheet layers 22 and two high temperatureresistant material coating or interleaf layers 24 which are each locatedintermediate two of the insulation layers 22. The glass fiber insulationblanket layers and/or foam insulations sheet layers 22, along with thehigh temperature resistant material coating or interleaf layers 24, areencapsulated or enclosed within an envelope 26 and placed against oradjacent the skin 28, e.g. aluminum skin, of the aircraft fuselage 30.In both of the embodiments shown, the major surfaces of the insulationlayers 22 and the coating or interleaf layers 24 extend in planesparallel to or substantially parallel to each other and the majorsurfaces of the skin 28. The systems of FIGS. 1 and 2 could includeadditional insulation layers 22 and high temperature resistant materialcoating or interleaf layers 24.

[0011] In the embodiment of the burn through resistant system 20 shownin FIG. 3, the system 20 includes a plurality of glass fiber insulationblanket layers and/or foam insulation sheet layers 22; a first hightemperature resistant material coating or interleaf layer 24 locatedintermediate one of the insulation layers 22 and the envelope 26 on theouter or fuselage skin facing side (the flame facing side) of thesystem; and a second high temperature resistant material coating orinterleaf layer 24 located intermediate two of the insulation layers 22.An envelope 26 encapsulates or encloses the insulation layers 22 andcoating or interleaf layers 24. The system 20 is placed against oradjacent the skin 28, e.g. aluminum skin, of the aircraft fuselage 30with the portion of the envelope covering the first coating or interleaflayer 24 of high temperature resistant material adjacent the skin 28 ofthe aircraft. As with the embodiments of FIGS. 1 and 2, the majorsurfaces of the insulation layers 22 and the coating or interleaf layers24 extend in planes parallel to or substantially parallel to each otherand the major surfaces of the fuselage skin 28. While not shown in FIG.3, additional coating or interleaf layers 24 of high temperatureresistant material can be included intermediate the insulation layers22.

[0012] Preferably, the glass fiber blanket layers 22 are one inch (25.4mm) thick Microlite AA glass fiber insulation blankets (manufactured andsold by Johns Manville International, Inc.) having densities of about0.42 pcf (6.7 Kg/m³) or one inch (25.4 mm) thick Premium NR glass fiberinsulation blankets (manufactured and sold by Johns ManvilleInternational, Inc.) having densities of about 0.34 pcf (5.4 Kg/m³).Preferably, the foam insulation layers 22 are one inch (25.4 mm) thickpolyimide foam insulation layers having densities of about 0.3 pcf (4.8Kg/m³) to about 0.6 pcf (9.6 Kg/m³).

[0013] Preferably, the high temperature resistant coating or interleaflayer or layers 24 include a reflective plate-like mineral, such as butnot limited to vermiculite, applied in a coating to or incorporated intoone or both major surfaces of a sheet, such as a paper sheet, an organicfiber mat, a glass fiber mat, or a fabric sheet. The high temperatureresistant coating or interleaf layers 24 can also be applied as acoating directly to one or more of the major surfaces of the insulationlayers 22. One example of an interleaf layer 24 includes a paper likeproduct, such as Manninglas 1208 paper (manufactured by LydallCorporation) made from 6.5 micron DE glass (little or no binder is usedto produce the paper) and vermiculite which is applied as a coating onone or both sides or major surfaces of the paper sheet. An interleaflayer 24 of Manninglas 1208 paper coated on both sides weighs 13.8 g/ft²(148 g/m² . An insulation system 20 using three layers 24 of 0.34Premium NR fiber glass blanket to sandwich two layers of Manninglas 1208paper weighs about 66 g/ft² (710 g/m²) (the weight of the aluminumfuselage skin is not included). Another example of an interleaf layer 24includes a spunlaced fabric, such as Freudenberg C1999VM aircraft seatcushion fire block fabric made from 70% Curlon partially oxidized PANfiber and 30% Kynar phenolic fiber and zig-zag stitched with a hightemperature resistant organic fiber, and vermiculite which is applied asa coating to one or both sides or major surfaces of the fabric. A burnthrough resistant system 20 of the present invention using one interleaflayer of Freudenberg C1999VM fabric coated with a vermiculite coatingand sandwiched between two outboard fiber glass or polyimide foam layers22 is considered tough enough to withstand the air pressure fluctuationsattributed to a pulsing flame front or wind and provides greater than 7minutes of burn through resistance. This embodiment of the system 20,using three layers 22 of 0.42 pcf (6.7 Kg/m³) Microlite AA glass fiberblanket and one interleaf layer 24 of vermiculite coated FreudenbergC1999VM fabric weighs about 62.5 g/ft² (672 g/m²) (the weight of thealuminum fuselage skin is not included). Due to the desire to keepaircraft fuselages as light as practical, the systems 20 of the presentinvention preferably weigh less than 70 g/ft² (753 g/m²) not includingthe weight of the fuselage skin.

[0014] Preferably, the encapsulating envelope 26 is a polymeric filmenvelope, such as but not limited to a Mylar film or a polyimide filmenvelope with a polyimide film envelope being preferred since the use ofsuch an envelope extends the burn through time when compared to a Mylarfilm envelope. Two burn through resistant systems were tested using thesame core materials, but with different film envelopes. A three layersystem of 0.42 pcf (6.7 Kg/m³) Microlite AA glass fiber blankets wastested with a Mylar film covering and also with a polyimide filmcovering (System configuration I). A three layer system of ANSC carbonfiber blanket and two layers of 0.42 pcf (6.7 Kg/m³) Microlite AA glassfiber blankets was also tested with a Mylar film covering and also witha polyimide film covering (System configuration II). With Systemconfiguration I, the burn through time using the Mylar film covering wasabout 2.67 minutes and the burn through time using the polyimide filmcovering was about 3.25 minutes. With System configuration II, the burnthrough time using the Mylar film covering was about 4.25 minutes andthe burn through time using the polyimide film covering was about 8.50minutes. Thus, in both tests, the system covered with the polyimide filmexhibited a longer burn through time.

[0015] The term “burn through time” as used in this specification andclaims relates to a test method developed by Johns ManvilleInternational, Inc. and is based on an ASTM E-119 test rig. This ASTMtest method is a standard one for fire tests of building constructionand materials. The test sample is 73.7 cm×73.7 cm square and is testedin a vertical configuration. The sample itself is made up of a “system”consisting of a 1.6 mm thick aluminum skin to the fire side and theinsulation batting enclosed in covering films of various types. Thesample does not include an interior trim panel as part of the fuselageconstruction. The system sample is subjected to a furnace with a heatflux of 12 to 15 W/cm² and a temperature of 1093° C. The test beginswhen a sliding door separating the furnace from the system test sampleis removed. The time of failure back to the back or cold side coveringfilm is recorded, and the “burn through time” is deemed to be when theflame reaches or penetrates to the cold side.

[0016] Initial test results from this method showed that aluminum skinon its own achieved an approximate failure time of one minute. Thestandard configuration of three layers of 0.42 pcf (6.7 Kg/m³) MicroliteAA glass fiber blanket encased in Mylar film (System configuration I)yielded a result of 2.67 minutes to burn through. A system consisting ofa layer of carbon fiber batting and two layers of fiber glassencapsulated in polyimide film (System configuration II) yielded a burnthrough time of 8.55 minutes in the above described Johns ManvilleInternational, Inc. test apparatus. These results show good relativeranking with the full scale FAA results for burn through time.

[0017] The system 20 of the present invention preferably has a burnthrough time of at least 5 minutes and more preferably, 7 minutes. Asystem 20 of the present invention including three insulation layers 22of 0.42 pcf×1 inch (6.7 Kg/m³×25.4 mm) Microlite AA glass fiber blanketand two interleaf layers 24 of 40 mil Manninglas 1208 glass fiber matcoated on both sides with vermiculite, encapsulated within AN47R Mylarfilm, exhibited a burn through time of greater than 10:00 minutes (filmfailure at 5:00 minutes; test stopped after 10:00 minutes). A system 20of the present invention including two outer insulation layers 22 of0.42 pcf×1 inch (6.7 Kg/m³×25.4 mm) Microlite AA glass fiber blanket, anintermediate layer 22 of 0.3 pcf×1 inch (4.8 Kg/m³×25.4 mm) Aero-midepolyimide foam and two interleaf layers 24 of 40 mil Manninglas 1208glass fiber mat coated on both sides with vermiculite, encapsulatedwithin AN47R Mylar film, exhibited a burn through time of 10:00 minutes(film failure at 4:38 minutes; excessive smoke from foam; test stoppedafter 10:00 minutes). A system 20 of the present invention includingthree insulation layers 22 of 0.42 pcf×1 inch (6.7 Kg/m³×25.4 mm)Microlite AA glass fiber blanket and two interleaf layers 24 of 0.015inch (0.38 mm) Manninglas 1208 glass fiber mat knife coated withvermiculite, encapsulated within Insulfab 240 Mylar film, exhibited aburn through time of greater than 10:00 minutes (film failure at 3:54minutes; standard smoke; glowing mat at 5:21 minutes; test stopped after10:00 minutes). A system 20 of the present invention including two outerinsulation layers 22 of 0.42 pcf×1 inch (6.7 Kg/m³×25.4 mm) Microlite AAglass fiber blanket, an intermediate layer 22 of 0.3 pcf×1 inch (4.8Kg/m³×25.4 mm) Aero-mide polyimide foam and two interleaf layers 24 of0.015 inch (0.38 mm) Manninglas 1208 glass fiber mat knife coated withvermiculite, encapsulated within an Insulfab 240 Mylar film, exhibited aburn through time of greater than 10:00 minutes (film failure at 4:04minutes; medium smoke; glowing mat at 6:10; test stopped after 10:00minutes). A system 20 of the present invention including threeinsulation layers 22 of 0.42 pcf×1 inch (6.7 Kg/m³×25.4 mm) Microlite AAglass fiber blanket and two interleaf layers 24 of Freudenberg C1999 VM200 grams/m² fabric coated with vermiculite, encapsulated withinInsulfab 240 Mylar film, exhibited a burn through time of 10:24 minutes(film failure at 7:40 minutes; glowing mat exposed at 8:21 minutes; teststopped after 10:24 minutes).

[0018] In describing the invention, certain embodiments have been usedto illustrate the invention and the practices thereof. However, theinvention is not limited to these specific embodiments as otherembodiments and modifications within the spirit of the invention willreadily occur to those skilled in the art on reading this specification.Thus, the invention is not intended to be limited to the specificembodiments disclosed, but is to be limited only by the claims appendedhereto.

What is claimed is:
 1. An insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, comprising: an encapsulated multilayered insulation composite; the multilayered insulation composite including a first insulation layer, a second insulation layer, and a first interleaf layer of a high temperature resistant material; the insulation layers and the interleaf layer each having major surfaces extending in planes substantially parallel to each other and being enclosed within a film.
 2. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 1, wherein: the interleaf layer comprises a reflective mineral.
 3. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 2, wherein: the interleaf layer comprises a reflective mineral coated sheet.
 4. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 2, wherein: the insulation layers are glass fiber insulation layers; and the multilayered insulation composite is encapsulated within a polymeric film.
 5. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 4, wherein: the polymeric film is a polyimide film.
 6. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 4, wherein: the multilayered insulation composite has a burn through time of at least 5 minutes.
 7. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 2, wherein: the insulation layers are polyimide foam insulation layers; and the multilayered insulation composite is encapsulated within a polymeric film.
 8. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 7, wherein: the polymeric film is a polyimide film.
 9. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 7, wherein: the multilayered insulation composite has a burn through time of at least 5 minutes.
 10. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 2, wherein: the first interleaf layer is intermediate the major surfaces of the first and second insulation layers which are opposed to each other.
 11. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 10, wherein: the multilayered insulation composite includes a third insulation layer and a second interleaf layer of a high temperature resistant material; the third insulation layer and the second interleaf layer each have major surfaces extending in planes substantially parallel to the major surfaces of the first and second insulation layers and the first interleaf layer; and the second interleaf layer is intermediate the major surfaces of the second and third insulation layers which are opposed to each other.
 12. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 1, wherein: the first interleaf layer of a high temperature resistant material is intermediate an outer major surface of the first insulation layer and the film.
 13. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 12, wherein: a second interleaf layer of high temperature resistant material is intermediate the major surfaces of the first and the second insulation layers which are opposed to each other.
 14. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 12, wherein: there is a third insulation layer and a second interleaf layer of high temperature resistant material which is intermediate the opposed major surfaces of two of the insulation layers.
 15. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 12, wherein: the interleaf layer comprises a reflective mineral.
 16. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 15, wherein: the interleaf layer comprises a reflective mineral coated sheet.
 17. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 12, wherein: the insulation layers are glass fiber insulation layers; and the multilayered insulation composite is encapsulated within a polymeric film.
 18. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 17, wherein: the polymeric film is a polyimide film.
 19. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 17, wherein: the multilayered insulation composite has a burn through time of at least 5 minutes.
 20. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 12, wherein: the insulation layers are foam insulation layers; and the multilayered insulation composite is encapsulated within a polymeric film.
 21. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 16, wherein: the foam is a polyimide foam and the polymeric film is a polyimide film.
 22. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 19, wherein: the multilayered insulation composite has a burn through time of at least 5 minutes.
 23. An aircraft fuselage having an outer skin and an insulation system for increasing the burn through resistance of the aircraft fuselage, comprising: an encapsulated multilayered insulation composite adjacent an inner major surface of the outer fuselage skin; the multilayered insulation composite including a first insulation layer, a second insulation layer, and an interleaf layer of a high temperature resistant material; the insulation layers and the interleaf layer each having major surfaces extending in planes substantially parallel to each other and the inner major surface of the metallic skin and being enclosed within a film.
 24. The aircraft fuselage according to claim 23, wherein: the interleaf layer comprises a reflective mineral.
 25. The aircraft fuselage according to claim 24, wherein: the interleaf layer comprises a reflective mineral coated sheet.
 26. The aircraft fuselage according to claim 23, wherein: the insulation layers are glass fiber insulation layers; and the multilayered insulation composite is encapsulated within a polymeric film.
 27. The aircraft fuselage according to claim 23, wherein: the insulation layers are foam insulation layers; and the multilayered insulation composite is encapsulated within a polymeric film.
 28. The aircraft fuselage according to claim 23, wherein: the multilayered insulation composite has a burn through time of at least 5 minutes.
 29. The aircraft fuselage according to claim 23, wherein: the first interleaf layer is intermediate the major surfaces of the first and second insulation layers which are opposed to each other.
 30. The aircraft fuselage according to claim 29, wherein: the interleaf layer comprises a reflective mineral.
 31. The aircraft fuselage according to claim 29, wherein: the multilayered insulation composite includes a third insulation layer and a second interleaf layer of a high temperature resistant material; the third insulation layer and the second interleaf layer each have major surfaces extending in planes substantially parallel to the major surfaces of the first and second insulation layers and the first interleaf layer; and the second interleaf layer is intermediate the major surfaces of the second and third insulation layers which are opposed to each other.
 32. The aircraft fuselage according to claim 31, wherein: the interleaf layer comprises a reflective mineral.
 33. The aircraft fuselage according to claim 23, wherein: the first interleaf layer of a high temperature resistant material is intermediate an outer major surface of the first insulation layer and the film.
 34. The aircraft fuselage according to claim 33, wherein: the interleaf layer comprises a reflective mineral.
 35. The aircraft fuselage according to claim 33, wherein: a second interleaf layer of high temperature resistant material is intermediate the major surfaces of the first and the second insulation layers which are opposed to each other.
 36. The aircraft fuselage according to claim 35, wherein: the first and second interleaf layers comprise a reflective mineral.
 37. The aircraft fuselage according to claim 33, wherein: there is a third insulation layer and a second interleaf layer of high temperature resistant material which is intermediate the opposed major surfaces of two of the insulation layers.
 38. The aircraft fuselage according to claim 37, wherein: the first and second interleaf layers comprise a reflective mineral.
 39. An insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, comprising: an encapsulated insulation composite system; the insulation composite system including at least one insulation layer, and a barrier layer of a high temperature resistant reflective mineral material; the at least one insulation layer and the barrier layer each having major surfaces extending in planes substantially parallel to each other and the composite system being enclosed within a polymeric film.
 40. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 39, wherein: the polymeric film is a polyimide film.
 41. The insulation system for increasing the burn through resistance of an aircraft fuselage having an outer skin, according to claim 39, wherein: the barrier layer comprises a reflective mineral coated sheet. 